The present invention relates to an exhaust pipe for a supercharged multi-cylinder internal-combustion engine and, more particularly, to an interior pipe carrying hot exhaust gases and a housing which surrounds the interior pipe at a distance therefrom, is undivided in longitudinal and transverse directions and has a cooling water space constructed between an approximately cylindrical intermediate wall and a cylindrical shell which is sealingly supported on the intermediate wall, and the interior pipe being divided into individual sections in the longitudinal direction, each section of the interior pipe being configured approximately cylindrically from a rectangular sheet metal blank, and the intermediate wall having exhaust gas inlet openings. By way of an encapsulated exhaust pipe, it is achieved that the exhaust gas suffers an only minimal heat loss on its way from the cylinder to the supercharger aggregate, and thus a higher energy potential is available for the supercharging of the internal-combustion engine. In addition, the surface temperature of the exhaust pipe is in the range of the cooling water temperature of the internal-combustion engine, as required for some applications.
European Patent Document EP 0 469 171 A1 shows an exhaust pipe in which the sections of the interior pipe cause an almost complete encapsulation of the hot exhaust gases. The principal purpose of this arrangement is the protection of the intermediate wall from hot gas corrosion caused by exhaust gas. Although on one hand, the high-expenditure construction of the interior pipe permits the use of materials for the intermediate wall which have a low resistance against hot gas corrosion and minimizes the heat loss from the exhaust gas, it results, on the other hand, in excessive manufacturing expenditures for the interior pipe.
It is therefore an object of the present invention to provide an exhaust gas pipe having a simplified construction of the sections of the interior pipe to achieve a reduction of the manufacturing costs.
This object has been achieved according to the present invention by providing the intermediate wall is provided with webs extending radially inwardly, each section of the interior pipe supported on an interior contour of assignee webs, one of the sections of the interior pipe respectively has a C-shaped cross-section and is arranged with an opening sector opposite a respective one of the exhaust gas inlet openings, the other of the sections of the interior pipe are adjacent to the respective one of the exhaust gas inlet opening have an approximately circular cross-section, and longitudinal edges of the C-shaped sections of the interior pipe are operatively arranged, with stop edges constructed on the intermediate wall in the longitudinal direction to protect against torsional influences.
Principal advantages achieved with the present invention are that the support of each section of the interior pipe on webs on the intermediate wall results in an improvement of the form stability of the exhaust pipe in the case of stress caused by shock and vibration, that the C-shaped sections increase the absorbing power of the interior pipe for the hot gas shock load which is caused by the exhaust gases which periodically flow out of the exhaust ducts of the cylinders, and that a lowering of the manufacturing costs is achieved because of the simplified manufacturing of the sections of the interior pipe.